Geothermal studies in the McMurdo Sound region
Wales Stream have not yielded samples of A. colbecki.
Samples QL-137, QL-138, QL-139, QL-153, QL154, QL-155, QL-156, QL-157, QL-158, and QL-159 were collected near DVDP holes 8, 9, and 10; samples QL-162, QL-163, QL-164, and QL-165 were collected from the north shore of New Harbor (figure). All of these samples came from emerged, stratified sand-and-gravel deposits that possess irregular surface morphology and that commonly exhibit scattered internal and surficial glacial clasts. Except for their fossil content, these deposits generally cannot be differentiated readily from adjacent surficial glacial drift. Moreover, they were deposited contemporaneously with, and some occur adjacent to, the delta-like deposits described previously; this is shown not only by carbon-14 dates but by individual beds near sample site QL- 160 that can be traced from a deposit with large glacial clasts into a delta-like deposit that lacks clasts. None of the shell samples pinpoints an exact position of past relative sea level, because A. colbecki currently live on the floor of New Harbor at depths greater than 4 meters and are most common at about 25 meters (John Oliver, personal communication, 1975). However, the altitude and age of each sample affords a minimum value of emergence that has occurred since the date involved; actual emergence exceeded these minimum values, perhaps by substantial amounts. Hence, the table shows that emergence during the past 5,400 years has exceeded 8.1 meters. In addition to providing values of emergence, the dates afford minimum ages for deglaciation of New Harbor. We therefore dated the large number of samples listed in the table to reduce the possibility of overlooking the oldest shells. Our present explanation for fossil marine deposits at New Harbor involves the following events: During the youngest Ross Sea glaciation (Denton et al., 1971), an ice tongue projected westward from McMurdo Sound into Taylor Valley nearly as far as Suess Glacier, damming an extensive lake in the valley. Deposition of numerous deltas and minor moraines accompanied ice recession and concomitant lake-level lowering. The inland deltas along Wales Stream were deposited into a remnant of this lake dammed between the retreating ice margin near McMurdo Sound and the high threshold of unconsolidated sediments between Commonwealth Glacier and New Harbor. Southward recession of the grounding line of Ross Sea ice into McMurdo Sound accompanied ice-tongue recession from Taylor Valley. Hence, fossil sediments in the delta-like deposit at the mouth of Wales Stream indicate that both events had occurred at New Harbor by 6,670 carbon-14 years before present (QL-157). Most of the recog88
nized emergence, which exceeded 8.1 meters, occurred after 5,400 carbon-14 years before present (QL- 163) without concurrent formation of emerged beaches; although direct evidence is lacking at New Harbor, considerable emergence probably predated 5,400 carbon-14 years before present. One explanation for the absence of emerged beaches is that the floating McMurdo Ice Shelf projected northward into New Harbor until very recently, so that the emerged marine deposits were uplifted from beneath the shelf margin. In this case, the glacial clasts were dropped into fossiliferous sediments accumulating beneath the shelf, except locally where streamwater melted indentations into the margin of the shelf and hence precluded clasts from being dropped into fossiliferous, stratified sand accumulating at these sites. We thank Michael Chapman-Smith for pointing out several of the sample sites. This research was supported by National Science Foundation grant opp 75-20991. References Chapman-Smith, M., and P. G. Luckman. 1974. Late Cenozoic glacial sequence cored at New Harbor, Victoria Land, Antarctica (DVDP 8 and 9). In: Dry Valley Drilling Project (DVDP) Bulletin 3. DeKaib, Northern Illinois University. 120-147. Denton, G. H., R. L. Armstrong, and M. Stuiver. 1971. The Late Cenozoic glacial history of Antarctica. In: Late Cenozoic Ages (Turekian, K. K., editor). New Haven, Yale University Press. 267-306. McKelvey, B. C. 1974. Preliminary site reports, DVDP sites 10 and 11, Taylor Valley. In: Dry Valley Drilling Project (DVDP) Bulletin 5. DeKaib, Northern Illinois University. 16-60. Treves, S. B., and B. C. McKelvey. 1975. Drilling in Antarctica, September-December, 1974. In: Dry Valley Drilling Project (DVDP) Bulletin 5. DeKalb, Northern Illinois University. 4-10.
Geothermal studies in the McMurdo Sound region GERALD J . BUCHER and EDWARD R. DECKER Department of Geology The University of Wyoming Laramie, Wyoming 82071
Field research during the 1975-1976 austral summer focused on measurements of temperature in Dry Valley Drilling Project (DVDP) driliholes. Mr. ANTARCTIC JOURNAL
Bucher was in the field from 4 November 1975 to 8 January 1976. Most field work this season involved studies of DVDP holes that were drilled during previous summers. Data from these studies confirm earlier estimates (Pruss et al., 1974; Decker, 1974; Decker et al., 1975) for permafrost thicknesses near many of the sites. These estimates are as follows: 440 to 500 meters near hole 3, 800 to 970 meters near hold 6, 240 to 310 meters near holes 8 and 10, about 400 meters near hole 11, and about 360 meters near hole 12. The new data also support the propositions of Pruss et al. (1974), Decker (1974), and Decker et al. (1975) that previous field work yielded reliable estimates for equilibrium geothermal gradients in several of the holes. The best example is provided by measurements in hole 3 on Ross Island. Here the first set of measurements on 1 November 1973 and the last log on 31 December 1975 through 3 January 1976 yield least squares gradients in the 100- to 260-meter depth interval that agree to within 5 percent. A similar conclusion is implied by data for holes 8, 11, and 12 in the dry valleys. Calculations based on the first and last sets of temperature measurements at these sites yield gradients that do not differ by more than 10 percent for the 30- to 135-meter interval in hole 8, for the 60- to 300-meter interval in hole 11, and for the 40- to 180-meter interval in hole 12. Holes 13 and 14 (Don Juan Pond and North Fork) were logged once during the 1975-1976 season. Because the temperature log obtained for lower portions of hole 13 is characterized by alternating high and very low gradients, there is good evidence for circulating groundwaters near this site (also see Decker et al., 1975). In contrast to negative gradients in the lower part of hole 14 on 19 January 1975 (Decker et al., 1975), measurements there on 25-26 November 1975 yielded positive gradients that range from 38° to 54°C per kilometer between 20 meters and the maximum accessible depth of 60 meters. These positive gradients, in turn, suggest that hole 14 can be used for heat flow calculations and imply that permafrost could extend locally to a depth of 350 to 360 meters. Hole 15, in the western part of McMurdo Sound, was logged three times in November 1975. On 17 November a temperature of about -1.1'C was measured in the bottom of the hole at a depth of 184 meters (62 meters subbottom). Although drilling had been stopped for only 6 hours, this measurement was very stable. Other temperature measurements in hole 15 were made shortly after drilling (-8 hours) on 21 and 22 November. The 21 November log reached a depth of 184 meters, whereas the 22 November one did not go below 180 meters because sediment had flowed up the hole after drilling. Measurements on the latter dates were very June 1976
stable and ranged from -1.90C in the waters just above the sea floor to 0.1°C at a depth of 180 meters (58 meters subbottom). The temperature was 0.3°C at 184 meters on 21 November, indicating a tem perature change of 1.4°C since the hole-bottom measurement on 17 November. Although the last two logs are characterized by high and variable gradients in lower portions of the hole, we defer discussion of their possible significance due to a lack of thermal conductivity data and the possibility that our measurements do not represent equilibrium temperatures. This research was supported by National Science Foundation grant o pp 72-05804. References Decker, E. R. 1974. Preliminary geothermal studies of the Dry Valley Drilling Project holes at McMurdo Station, Lake Vanda, Lake Vida, and New Harbor, Antarctica. In: Dry Valley Drilling Project Bulletin 4. DeKaib, Northern Illinois University. 22-23. Decker, E. R., K. H. Baker, and H. H. Harris. 1975. Geothermal studies in the dry valleys and on Ross Island. Antarctic Journal of the U.S., X(4): 176. Pruss, E. F., E. R. Decker, and S. B. Smithson. 1974. Preliminary temperature measurements at DVDP holes 3, 4, 6, and 8. Antarctic Journal of the U.S., IX (4): 133-134.
Hydrogeology in the dry valleys and HENRY HARRIS Illinois State Geological Survey Urbana, Illinois 61801
KEROS CARTWRIGHT
Hydrogeological studies of the two previous austral summers were continued during the 1975-1976 field season. With the exception of occasional visits to Taylor Valley and the Dry Valley Drilling Project (DVDP) McMurdo Sound site, all of our research was confined to the western half of Wright Valley. The field party included Mr. Harris (16 October 1975 to 30 January 1976), David L. Gross (27 October to 3 December 1975), Illinois State Geological Survey, and Michael Chapman-Smith (3 December 1975 to 30 January 1976), University of Auckland, New Zealand. Our project's first month in the field this season 89
Samples QL-137, QL-138, QL-139, QL-153, QL154, QL-155, QL-156, QL-157, QL-158, and QL-159 were collected near DVDP holes 8, 9, and 10; samples QL-162, QL-163, QL-164, and QL-165 were collected from the north shore of New Harbor (figure). All of these samples came from emerged, stratified sand-and-gravel deposits that possess irregular surface morphology and that commonly exhibit scattered internal and surficial glacial clasts. Except for their fossil content, these deposits generally cannot be differentiated readily from adjacent surficial glacial drift. Moreover, they were deposited contemporaneously with, and some occur adjacent to, the delta-like deposits described previously; this is shown not only by carbon-14 dates but by individual beds near sample site QL- 160 that can be traced from a deposit with large glacial clasts into a delta-like deposit that lacks clasts. None of the shell samples pinpoints an exact position of past relative sea level, because A. colbecki currently live on the floor of New Harbor at depths greater than 4 meters and are most common at about 25 meters (John Oliver, personal communication, 1975). However, the altitude and age of each sample affords a minimum value of emergence that has occurred since the date involved; actual emergence exceeded these minimum values, perhaps by substantial amounts. Hence, the table shows that emergence during the past 5,400 years has exceeded 8.1 meters. In addition to providing values of emergence, the dates afford minimum ages for deglaciation of New Harbor. We therefore dated the large number of samples listed in the table to reduce the possibility of overlooking the oldest shells. Our present explanation for fossil marine deposits at New Harbor involves the following events: During the youngest Ross Sea glaciation (Denton et al., 1971), an ice tongue projected westward from McMurdo Sound into Taylor Valley nearly as far as Suess Glacier, damming an extensive lake in the valley. Deposition of numerous deltas and minor moraines accompanied ice recession and concomitant lake-level lowering. The inland deltas along Wales Stream were deposited into a remnant of this lake dammed between the retreating ice margin near McMurdo Sound and the high threshold of unconsolidated sediments between Commonwealth Glacier and New Harbor. Southward recession of the grounding line of Ross Sea ice into McMurdo Sound accompanied ice-tongue recession from Taylor Valley. Hence, fossil sediments in the delta-like deposit at the mouth of Wales Stream indicate that both events had occurred at New Harbor by 6,670 carbon-14 years before present (QL-157). Most of the recog88
nized emergence, which exceeded 8.1 meters, occurred after 5,400 carbon-14 years before present (QL- 163) without concurrent formation of emerged beaches; although direct evidence is lacking at New Harbor, considerable emergence probably predated 5,400 carbon-14 years before present. One explanation for the absence of emerged beaches is that the floating McMurdo Ice Shelf projected northward into New Harbor until very recently, so that the emerged marine deposits were uplifted from beneath the shelf margin. In this case, the glacial clasts were dropped into fossiliferous sediments accumulating beneath the shelf, except locally where streamwater melted indentations into the margin of the shelf and hence precluded clasts from being dropped into fossiliferous, stratified sand accumulating at these sites. We thank Michael Chapman-Smith for pointing out several of the sample sites. This research was supported by National Science Foundation grant opp 75-20991. References Chapman-Smith, M., and P. G. Luckman. 1974. Late Cenozoic glacial sequence cored at New Harbor, Victoria Land, Antarctica (DVDP 8 and 9). In: Dry Valley Drilling Project (DVDP) Bulletin 3. DeKaib, Northern Illinois University. 120-147. Denton, G. H., R. L. Armstrong, and M. Stuiver. 1971. The Late Cenozoic glacial history of Antarctica. In: Late Cenozoic Ages (Turekian, K. K., editor). New Haven, Yale University Press. 267-306. McKelvey, B. C. 1974. Preliminary site reports, DVDP sites 10 and 11, Taylor Valley. In: Dry Valley Drilling Project (DVDP) Bulletin 5. DeKaib, Northern Illinois University. 16-60. Treves, S. B., and B. C. McKelvey. 1975. Drilling in Antarctica, September-December, 1974. In: Dry Valley Drilling Project (DVDP) Bulletin 5. DeKalb, Northern Illinois University. 4-10.
Geothermal studies in the McMurdo Sound region GERALD J . BUCHER and EDWARD R. DECKER Department of Geology The University of Wyoming Laramie, Wyoming 82071
Field research during the 1975-1976 austral summer focused on measurements of temperature in Dry Valley Drilling Project (DVDP) driliholes. Mr. ANTARCTIC JOURNAL
Bucher was in the field from 4 November 1975 to 8 January 1976. Most field work this season involved studies of DVDP holes that were drilled during previous summers. Data from these studies confirm earlier estimates (Pruss et al., 1974; Decker, 1974; Decker et al., 1975) for permafrost thicknesses near many of the sites. These estimates are as follows: 440 to 500 meters near hole 3, 800 to 970 meters near hold 6, 240 to 310 meters near holes 8 and 10, about 400 meters near hole 11, and about 360 meters near hole 12. The new data also support the propositions of Pruss et al. (1974), Decker (1974), and Decker et al. (1975) that previous field work yielded reliable estimates for equilibrium geothermal gradients in several of the holes. The best example is provided by measurements in hole 3 on Ross Island. Here the first set of measurements on 1 November 1973 and the last log on 31 December 1975 through 3 January 1976 yield least squares gradients in the 100- to 260-meter depth interval that agree to within 5 percent. A similar conclusion is implied by data for holes 8, 11, and 12 in the dry valleys. Calculations based on the first and last sets of temperature measurements at these sites yield gradients that do not differ by more than 10 percent for the 30- to 135-meter interval in hole 8, for the 60- to 300-meter interval in hole 11, and for the 40- to 180-meter interval in hole 12. Holes 13 and 14 (Don Juan Pond and North Fork) were logged once during the 1975-1976 season. Because the temperature log obtained for lower portions of hole 13 is characterized by alternating high and very low gradients, there is good evidence for circulating groundwaters near this site (also see Decker et al., 1975). In contrast to negative gradients in the lower part of hole 14 on 19 January 1975 (Decker et al., 1975), measurements there on 25-26 November 1975 yielded positive gradients that range from 38° to 54°C per kilometer between 20 meters and the maximum accessible depth of 60 meters. These positive gradients, in turn, suggest that hole 14 can be used for heat flow calculations and imply that permafrost could extend locally to a depth of 350 to 360 meters. Hole 15, in the western part of McMurdo Sound, was logged three times in November 1975. On 17 November a temperature of about -1.1'C was measured in the bottom of the hole at a depth of 184 meters (62 meters subbottom). Although drilling had been stopped for only 6 hours, this measurement was very stable. Other temperature measurements in hole 15 were made shortly after drilling (-8 hours) on 21 and 22 November. The 21 November log reached a depth of 184 meters, whereas the 22 November one did not go below 180 meters because sediment had flowed up the hole after drilling. Measurements on the latter dates were very June 1976
stable and ranged from -1.90C in the waters just above the sea floor to 0.1°C at a depth of 180 meters (58 meters subbottom). The temperature was 0.3°C at 184 meters on 21 November, indicating a tem perature change of 1.4°C since the hole-bottom measurement on 17 November. Although the last two logs are characterized by high and variable gradients in lower portions of the hole, we defer discussion of their possible significance due to a lack of thermal conductivity data and the possibility that our measurements do not represent equilibrium temperatures. This research was supported by National Science Foundation grant o pp 72-05804. References Decker, E. R. 1974. Preliminary geothermal studies of the Dry Valley Drilling Project holes at McMurdo Station, Lake Vanda, Lake Vida, and New Harbor, Antarctica. In: Dry Valley Drilling Project Bulletin 4. DeKaib, Northern Illinois University. 22-23. Decker, E. R., K. H. Baker, and H. H. Harris. 1975. Geothermal studies in the dry valleys and on Ross Island. Antarctic Journal of the U.S., X(4): 176. Pruss, E. F., E. R. Decker, and S. B. Smithson. 1974. Preliminary temperature measurements at DVDP holes 3, 4, 6, and 8. Antarctic Journal of the U.S., IX (4): 133-134.
Hydrogeology in the dry valleys and HENRY HARRIS Illinois State Geological Survey Urbana, Illinois 61801
KEROS CARTWRIGHT
Hydrogeological studies of the two previous austral summers were continued during the 1975-1976 field season. With the exception of occasional visits to Taylor Valley and the Dry Valley Drilling Project (DVDP) McMurdo Sound site, all of our research was confined to the western half of Wright Valley. The field party included Mr. Harris (16 October 1975 to 30 January 1976), David L. Gross (27 October to 3 December 1975), Illinois State Geological Survey, and Michael Chapman-Smith (3 December 1975 to 30 January 1976), University of Auckland, New Zealand. Our project's first month in the field this season 89
